This application claims the benefit of Danis Application No. 200 00836 filed May 26, 2000 and PCT/DK01/00371 filed May 28, 2001.
The present invention concerns a plant for the cleaning of new or used metal parts by so-called wet blasting, namely for degreasing and cleaning of relatively small metal items which are suitable for handling in, for example, drum-like cleaning chambers. Such wet-blasting plants, which in a very effective manner work with a mixture of water and cleaning granulate, are known in different configurations, but the plant according to the invention is so special and advantageous that it is not considered necessary to describe the known technique in further detail.
In brief, it must be mentioned that the relevant technique is not particularly problematic with regard to the actual main task of executing a spraying of the blasting medium on the items, but rather in arranging this in both an effective and operationally economic manner in a recirculation plant for good utilisation of the blasting medium. Depending on its character and wearing qualities, the blasting medium can be reused over shorter or longer periods. However, it will gradually be worn down to such small grain sizes that this fraction will be ineffective in the recirculation process, and therefore must preferably be separated from the blasting medium, i.e. the mixture of liquid (water) and blasting medium. Moreover, the dirt which is removed from the items by the cleaning should be separated from this medium, and at least from time to time there must be effected a certain addition of new blasting medium in order to keep the plant fully effective.
In this connection, a number of part-problems exist which constitute bottlenecks in the overall process, and with the invention it is endeavoured to provide a method and respectively a processing plant which with simple means can ensure an expedient overall function which, by and large, operates in a continuous manner.
On this basis, the invention comprises a combination of various procedures which, although separately can be varied within certain frameworks, collectively must be considered as being necessary and adequate for solving the tasks presented. It will herewith be of minor significance for the novelty aspect of the invention whether some of the relevant procedures should be known, in so much as they are new in the overall combination according to the invention.
The invention is based on the consideration that an advantageous working procedure can be achieved by dividing the plant into some discrete units for solving part-problems as follows:
1) A processing chamber in which on a movable support the items are exposed to a spraying by the blasting medium from an overlying, downwardly-emitting arrangement for this medium;
2) An underlying collection tank for the collection of the sprayed-on blasting medium with its content of dirt cleaned from the items, and for precipitation of the heavier particles of the medium therein;
3) A transport arrangement such as a worm conveyor for the feeding of the precipitated material up and along an inclined bottom of this tank to an upper bottom outlet.
4) A sedimentation tank for receiving the overflow medium from the collection tank for separation of lighter material fractions from the overflow medium via a filter for the draining off of liquid;
5) A pump for the sucking of surface liquid from the sedimentation tank for pumping further through a pressure pipe to the medium-spraying arrangement in the processing chamber, and
6) An ejector unit inserted in this pressure pipe for the sucking of the concentrated blasting medium from said upper bottom outlet of the collection tank.
With this combination, work can be carried out with a continuous two-stage separation of the lighter material fractions, while maintaining high efficiency and good reusability of the fraction of the blasting medium which has not been worn down.